Structural Organisation in Animals

In multicellular animals, a group of similar cells along with intercellular substances performing a specific function forms a tissue. There are four basic types. Epithelial tissue may be simple (squamous, cuboidal, columnar and ciliated), compound or glandular, with cell junctions (tight, adhering and gap junctions). Connective tissue includes loose tissue (areolar and adipose), dense regular and irregular tissue, and specialised tissue (cartilage, bone and blood). Muscle tissue is skeletal, smooth or cardiac, the last with intercalated discs. Neural tissue is made of neurons and neuroglia. Tissues combine to form organs and organ systems. The chapter then studies the frog, Rana tigrina, as an example of organ systems in a vertebrate. Frogs are cold-blooded, show aestivation and hibernation, and can change colour for camouflage. You will learn their external features, such as the nictitating membrane, tympanum, and webbed hind limbs, and their digestive, respiratory (cutaneous, buccal and pulmonary), circulatory (three-chambered heart with hepatic and renal portal systems), excretory, nervous and reproductive systems. Frogs show external fertilisation, and their development includes a tadpole larva that undergoes metamorphosis.

Detailed Worksheet: Structural Organisation in Animals Section A - Definitions (10 marks) 1. What is a tissue? Name the four basic types of animal tissues. (2 marks) 2. What are the functions of tight junctions and gap junctions? (2 marks) 3. Distinguish between tendons and ligaments. (2 marks) 4. What are intercalated discs? Where are they found? (2 marks) 5. What are aestivation and hibernation? Why do frogs show them? (2 marks) Section B - Calculations and Applications (15 marks) 6. Neuroglia make up more than half the volume of neural tissue. If a sample of neural tissue has a volume of 40 cubic mm and neuroglia make up 55% of it, calculate the volume occupied by neurons. State two functions of neuroglia. (3 marks) 7. A female frog lays about 2,500 to 3,000 eggs at a time. If 2,800 eggs are laid and only 5% survive to become adult frogs, calculate the number of adults. Why do frogs lay so many eggs? (3 marks) 8. A frog's forelimb has 4 digits and its hindlimb 5 digits. Calculate the total number of digits. State two adaptations of the hind limbs for swimming and jumping. (3 marks) 9. A frog has 10 pairs of cranial nerves. Calculate the total number of cranial nerves. Name the parts of the frog's brain. (3 marks) 10. A frog's heart beats 40 times per minute at 20 degrees C and the rate drops to 10 per minute in winter. Calculate the percentage fall. Why does a frog's metabolic rate change with temperature? (3 marks) Section C - Diagrams (10 marks) 11. Draw labelled diagrams of simple squamous, cuboidal and columnar epithelium. (4 marks) 12. Draw a labelled diagram of the internal organs of a frog showing the complete digestive system. (3 marks) 13. Draw a labelled diagram of the male reproductive system of a frog. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Compare the three types of muscle tissue in terms of structure, location and control. Why is cardiac muscle not fatigued easily? (5 marks) 15. Explain how the frog is adapted to life both on land and in water, with reference to its respiration, skin and limbs. (5 marks) 16. Compare bone and cartilage. Explain the structure of compact bone and the role of osteocytes and chondrocytes. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw diagrams neatly with labels. Show calculation steps.